Purpose: :
Microbial contamination of contact lenses is the greatest riskfactor for corneal infection and likely inflammation. This studydetermined which clinical factors are associated with bacterialcontamination of silicone hydrogel contact lenses when wornfor continuous wear.

Methods: :
205 patients were enrolled in the LASH Contact Lens Study andwere fitted with lotrafilcon A lenses for monthly continuouswear and followed for 1 year. Lenses were aseptically removedafter 1 week and 4 months of wear and cultured using an agarsandwich technique. Lids and conjunctiva were routinely culturedat baseline, 1 week, and 4 months. Lenses were considered tohave abnormal microbiota when they harbored high levels of normalflora or other pathogenic organisms. Univariate analyses wereconducted to examine whether abnormal levels of lid or conjunctivalorganisms, lid disease, ethnicity, gender, age, history of previousadverse events, previous lens experience, lens deposits, cornealstaining, dry eye, or discomfort were associated with lens contamination.Significant variables were entered into a multivariable logisticregression model.

Results: :
33.3% of patients had sterile lenses in both eyes across multiplevisits. 31.7% of patients had significant levels of microbialcontamination on at least one lens across multiple visits. 53.7%and 11.2% of patients had significant levels of lid and conjunctivalcontamination, respectively, and 11.2% complained of discomfort.In univariate analyses, high levels or pathogenic lid and conjunctivalbiota, Asian ethnicity (protective), and lens discomfort wereassociated with lens bacterial contamination (p<0.05). Inmultivariable analysis, high levels or pathogenic lid and conjunctivalbiota (p=0.0263, p=0.0013, respectively), and lens discomfort(p=0.0199) were associated with abnormal lens microbial contamination.Although blepharitis was associated with lid microbial contamination(p=0.009), it was not associated with lens contamination.

Conclusions: :
As expected, lid and conjunctival microbiota are significantlyassociated with and likely the major route for lens contamination.This is the first study to report lens discomfort to also beassociated with abnormal levels of bacteria isolated from continuouswear contact lenses.